The present invention is concerned primarily with improvements in the performance of so-called two roll compactors, such as are in widespread commercial use for the compressive shrinkage treatment of tubular knitted fabrics. In this respect, the features of the invention are particularly useful in conjunction with apparatus of the type reflected in the prior Eugene Cohn et al. U.S. Pat. Nos. 3,015,145, 3,015,146 and 3,083,435. The equipment disclosed in these patents is intended primarily, although not necessarily exclusively, for the compressive shrinkage treatment of tubular knitted fabrics, to produce finished fabric and garments having minimum residual shrinkage characteristics. In general, the equipment described in the before mentioned patents includes a pair of rollers arranged in opposed relation and forming a compacting nip. One of the rollers is considered a feeding roller and the other a retarding roller, the latter having a surface speed which is controllably slower than that of the feeding roller. In accordance with principles expressed in the patents, fabric is typically laterally distended and steamed, and then delivered into surface contact with the feeding roller. The fabric is lightly confined against the surface of the feeding roller by means of a curved shoe, so that the fabric is driven in a relatively positive manner toward the roller nip formed by the opposed feeding and retarding rollers.
As the incoming fabric approaches the roller nip, it emerges from under the confining surface formed by the shoe. In accordance with the teachings of the above mentioned patents, the downstream or discharge end of the shoe is formed into a relatively sharp, blade-like edge or tip, which extends across the full width of the shoe and forms a sharp line of demarcation. The tip of this blade-like edge generally is located somewhere around one-quarter inch upstream from the roller nip and defines the upstream end of a compressive shrinking zone. The downstream end is, of course, defined by the roller nip, and opposed sides of the zone are defined by the roller surfaces themselves in the region between the shoe tip and the roller nip.
In general, in the operation of the compressive shrinkage equipment described, fabric is driven in a feeding direction by the feeding roller, until the fabric emerges from underneath the blade-like shoe tip and enters the compressive shrinking zone. In that zone, the fabric is decelerated to a speed determined by the slower surface speed of the retarding roller, whose surface is constituted to have a somewhat greater frictional grip on the fabric than does the feeding roller, in the region of the roller nip. Since the fabric is entering the compression zone at a higher rate of speed than it leaves, the fabric necessarily is compressed lengthwise in the zone. As the longitudinally compressed fabric passes through the roller nip, it is subjected to heat and localized rolling pressure, which stabilizes the fabric in its longitudinally compressed condition.
Among the various machine adjustments that can significantly affect the processing of the fabric in the compressive shrinking operation, an important one is the control of the length of the compressive shrinking zone, as determined by the spacing of the shoe tip from the roller nip. This spacing can be quite critical, and in practice it is adjusted with considerable precision.
Although the fabric processing operation often is highly sensitive to variation in the length of the compressive shrinking zone, adjustment of the zone has in the past been relatively difficult and time consuming with existing equipment, largely because of the need for meeting co-existing requirements of ruggedness and precision. Thus, in most cases, it has been necessary to stop the equipment before making an adjustment, and in any case the adjustment was sufficiently complex and time consuming as to tend to discourage a machine operator from making a minor adjustment, as might otherwise be indicated for greatest process optimization.
The present invention provides a novel, rugged and completely reliable precision adjustment mechanism, for controlling the length of the compressive shrinking zone, which enables the machine operator to adjust the zone with great precision, by means of a hand wheel or similar device located on the control side of the machine. The arrangement is such that the operator can, by a simple one hand manipulation, make precision changes in the compression zone length while the equipment is in operation and the operator is thus able to observe immediately the effect of the adjustment on the fabric emerging from the roller nip. With this arrangement, an experienced machine operator can easily optimize the performance of the equipment, as appropriate to accommodate various types and weights of fabric, different fibers and constructions, and other variables in the process.
In accordance with another feature of the invention, an advantageous form of shoe tip adjustment mechanism is provided which is largely compatible with standard forms of equipment now in the field. Accordingly, much of the existing equipment can be retrofitted with the new adjustment feature, enabling a significant upgrading in the performance of already existing installations of two roll compactor equipment of the type contemplated herein.
For a better understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description and to the accompanying drawings.